High-power microwave system based on modular loop line

Abstract

The invention relates to the technical field of pulse power, and discloses a high-power microwave system based on a modular loop line, and the system comprises a pulse power source which is formed by axially connecting 15 PFN modules in series, and a PFN tank body is arranged outside the PFN modules formed by connecting in series; the PFN module comprises a coil assembly, a low-voltage electrode, a high-voltage electrode, an insulator and an elastic pad, the coil assembly comprises three involute type coaxial cables, the three involute type coaxial cables are symmetrically distributed on the three-directional low-voltage electrode at 120 degrees, and the high-voltage electrode locks an inner conductor of the cable through a metal connecting sleeve of a thread fastening structure; the low-voltage electrode is communicated with a cable outer conductor through an outer conductor connecting sleeve of a thread fastening structure, and an elastic pad made of ethylene propylene diene monomer is placed between the high-voltage electrode and the coil assembly. According to the invention, the defect of low withstand voltage of the traditional coaxial cable is completely overcome, the problems of large size and heavy weight of the traditional high-power microwave equipment are solved, the high-power microwave equipment is light and small, and the maneuverability of the equipment is improved.

Description

Technical Field

[0001] This invention relates to the field of pulsed power technology, and more specifically, to a high-power microwave system based on a modular loop line. Background Technology

[0002] A high-power microwave system consists of a pulsed power source, high-power microwave devices, a directional transmitter, and a control system. Primary electrical energy is input to the repetitive pulsed power source, which converts it into a high-power, high-current pulsed relativistic electron beam. This provides electron pulses with voltages ranging from hundreds of thousands of volts to megavolts or more, beam currents in the tens of kiloamperes, pulse widths of tens of nanoseconds, and repetition frequencies exceeding 100 Hz. After conversion by the high-power microwave devices, microwave power ranging from hundreds of megawatts to several megawatts or more is generated. Microwave waveform control is primarily determined by the pulse formation method, including the forming line and switches, as well as the electron beam diodes.

[0003] Pulse forming lines are the source of microwave generation, providing high voltage electron beams for microwaves. The quality of the high-voltage pulse waveform plays a decisive role in the waveform and control of high-power microwaves. Currently, pulse forming lines mainly include single lines, coaxial lines, and spiral lines, but they suffer from problems such as excessive size and weight, excessively long axis length, and difficulty in optimization after forming, which have become bottlenecks restricting the development of high-power microwaves. Summary of the Invention

[0004] This invention provides a high-power microwave system based on a modular loop line, which solves the technical problems of large size and weight of traditional high-power microwave equipment in related technologies.

[0005] This invention provides a high-power microwave system based on a modular loop line, comprising:

[0006] The pulse power source consists of 15 PFN modules connected in series axially, with the PFN tank located outside the series-connected PFN modules;

[0007] The PFN module includes a coil assembly, a low-voltage electrode, a high-voltage electrode, an insulator, and an elastic pad. The coil assembly includes three involute coaxial cables, which are symmetrically distributed at 120° and welded to the three-way low-voltage electrode. The high-voltage electrode is crimped and locked to the inner conductor of the cable through an insert-type metal connecting sleeve. The low-voltage electrode is connected to the outer conductor of the cable through an outer conductor connecting sleeve with a threaded fastening structure. An elastic pad made of EPDM rubber is placed between the high-voltage electrode and the coil assembly. The elastic pad and the insulator together isolate the high-voltage and low-voltage electrodes.

[0008] The microwave generating system converts high-power electrical pulses from a pulse power source into high-power microwave energy and outputs it. The pulse power source is connected to the microwave generating system through an SF6 gas-filled tank.

[0009] Furthermore, the coaxial cable includes an inner conductor, a film-wrapped insulation layer, and an outer sheath. The inner conductor is made of aluminum rod. The film-wrapped insulation layer consists of, from the inside out: an inner polyimide film insulation layer, a polypropylene film insulation layer, and an outer polyimide film insulation layer. The outer sheath covers the outer wall of the outer conductor.

[0010] Furthermore, the microwave generating system also includes a coil magnetic field, which is encapsulated inside an outer cylinder. The axial ends of the outer cylinder are clamped and fixed by coil magnetic field fastening flanges. The outer cylinder flange is welded to the end of the outer cylinder. The outer cylinder flange and the coil magnetic field mating flange are rigidly connected by bolts. The mating flange is embedded in the groove of the mating flange. A mating gasket is provided between the mating flange and the mating flange. The mating gasket is used for precise alignment and vacuum isolation.

[0011] Furthermore, the microwave generating system also includes a microwave source and coil magnetic field fastening flange, which passes through and engages with the coil magnetic field docking flange to lock the coil magnetic field to the outer shell of the microwave generating system and maintains coaxial positioning with the microwave source output waveguide and antenna interface flange. At the end of the microwave source output waveguide, the microwave source and antenna channel interface flange is connected to an antenna channel.

[0012] Furthermore, the microwave generation system also includes a spatial corrugated waveguide, which serves as the core channel for electron beam-microwave conversion. The front end of the spatial corrugated waveguide is connected to the microwave source output waveguide via a spatial pre-waveguide clamp. The outer wall of the spatial corrugated waveguide is inserted into the outer cylinder of the spatial waveguide, and the spatial corrugated waveguide is radially locked in a three-point evenly distributed manner by fasteners that pass through the waist-shaped grooves on the side wall of the outer cylinder of the spatial waveguide.

[0013] Furthermore, a tungsten needle cathode is axially inserted into the electron emitter from the end of the spatial corrugated waveguide, and the base of the spatial corrugated waveguide is suspended and fixed at the center of the spatial corrugated waveguide by two alumina ceramic electron emitter support rods.

[0014] Furthermore, the spatial corrugated waveguide is pressed together with the coil magnetic field mating gasket through the end flange, forming a vacuum seal and a synergistic effect zone of the magnetic-electric composite field.

[0015] Furthermore, the SF6 filling tank uses fluororubber sealing rings, and electrical isolation is achieved by PI insulating bushings and alumina ceramic rings.

[0016] Furthermore, the high-voltage pulse is transmitted to the graphite electron emitter via the electron emitter support rod. The graphite electron emitter generates an electron beam, which is accelerated in the vacuum diode cavity and then bombards the spatial ripple waveguide.

[0017] Furthermore, the spatial corrugated waveguide uses a double-channel metal "C"-shaped vacuum seal ring to maintain a vacuum of 10⁻⁴ Pa. When the electron beam moves in the spatial corrugated waveguide, its energy is converted into microwave energy through the interaction with the electromagnetic field inside the waveguide, generating microwaves of a specific frequency.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention is based on the simple structure, compact size, light weight, modular adjustment and optimization of the loop wire, which can be filled with gas or oil. It can solve the problems and defects of traditional coaxial cables, overcome the low withstand voltage of traditional coaxial cables, and solve the problems of large size and heavy weight of traditional high-power microwave equipment, thereby achieving the miniaturization of high-power microwave equipment and improving the mobility of the equipment. Attached Figure Description

[0020] Figure 1 This is a front view of the high-voltage solid-state pulse forming module of the present invention;

[0021] Figure 2 This is a cross-sectional view of the high-voltage solid-state pulse forming module of the present invention;

[0022] Figure 3 This is a cross-sectional view of the coil of the present invention;

[0023] Figure 4 This is an exploded perspective view of the coil of the present invention;

[0024] Figure 5 yes Figure 4 Front view of the high-voltage electrode in the middle;

[0025] Figure 6 yes Figure 4 Front view of the low-voltage electrode.

[0026] In the diagram: 100, PFN module; 110, low-voltage electrode; 120, insulator; 130, high-voltage electrode; 140, elastic pad; 150, coil assembly; 200, SF6 gas filling tank; 300, microwave generation system; 301, pulse power source interface flange; 302, concentric flange; 303, concentric bolt; 304, coil magnetic field mating flange; 305, coil magnetic field outer cylinder; 306, coil magnetic field; 307, coil magnetic field outer cylinder flange; 308, coil magnetic field fastening method. 309. Flange for connecting the magnetic field of the coil; 310. Flange for fastening the microwave source and the magnetic field of the coil; 400. Waveguide for output of the microwave source; 410. Flange for interface between the microwave source and the antenna channel; 313. Waveguide with spatial corrugations; 314. Fastener for the waveguide with spatial corrugations; 315. Front waveguide retainer ring; 316. Outer cylinder of the waveguide with spatial corrugations; 317. Electron emitter; 318. Coil magnetic field mating gasket; 319. Electron emitter support rod; 320. Output electrode of the ring switch; 500. PFN tank. Detailed Implementation

[0027] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0028] At least one embodiment of the present invention discloses a high-power microwave system based on a modular loop line, such as Figure 1 - Figure 6 As shown, it includes a pulse power source, which consists of 15 triple involute pulse forming network (PFN) modules connected in series axially, and is integrated into the microwave generation system 300 through an SF6 gas filling tank 200.

[0029] The core of the PFN module 100 lies in its coaxial cable using a high-energy-density organic thin film, which increases energy density by 25 times compared to traditional solutions.

[0030] The PFN module 100, in conjunction with a ring-shaped multi-stage gas switch and a polyimide (PI) insulation system, can output a high-voltage pulse of 1.125 MV with a pulse width of 30 ns and a leading edge of 5–7 ns, which can directly drive a microwave source electron gun.

[0031] The entire system weighs less than 500 kg, which is 97% lighter than traditional oil-based systems, meeting the vehicle platform's requirements for lightweight and high reliability.

[0032] The PFN module 100 includes a coil assembly 150, a low-voltage electrode 110, a high-voltage electrode 130, and an elastic pad 140. The coil assembly 150 includes three involute coaxial cables with a single cable outer diameter of 7.5 mm. The three involute coaxial cables are symmetrically distributed at 120° and welded to the three-way low-voltage electrode 110 to form a current sharing topology.

[0033] The high-voltage end adopts a modular series interface design, including an inner conductor pin and an outer conductor slot, which supports axial stacking of 15 PFN modules 100. The 15 PFN modules 100 are separated by grooved polyimide separators (groove depth 1.2mm, groove width 0.7mm). The introduction of grooved polyimide separators significantly improves the vacuum surface withstand voltage to 85kV / cm.

[0034] In the assembly of the PFN module 100, the high-voltage electrode 130 is crimped and locked to the inner conductor of the cable via an insert-type metal connecting sleeve; the low-voltage electrode 110 conducts to the outer conductor of the cable via an outer conductor connecting sleeve with a threaded fastening structure. The entire cable is wound into a coil assembly 150 with an involute trajectory and fixed to the end support sleeve.

[0035] An elastic pad 140 made of EPDM rubber is placed between the high-voltage electrode 130 and the coil assembly 150 to buffer mechanical stress. The elastic pad 140 and the polyimide (PI) insulator 120 together isolate the high-voltage and low-voltage electrodes 110, and PI tape is used to wrap the connecting sleeve area to strengthen local insulation. Both the low-voltage electrode 110 and the high-voltage electrode 130 are made of 7075 aluminum alloy with conductive anodized surface.

[0036] It should be noted that each coaxial cable consists of an inner conductor, a thin-film insulation layer, an outer conductor, and an outer sheath. The inner conductor is made of aluminum rod with a smooth, burr-free surface and an axial outer diameter error controlled within 0.01mm to ensure current carrying capacity and reduce weight.

[0037] The structure of the film-wrapped insulation layer is complex, consisting of the following layers from the inside out: an inner polyimide film insulation layer (4 layers, 0.1 mm thick), a polypropylene film insulation layer (the main body, consisting of hundreds of 10 μm films heat-shrinked and cured), and an outer polyimide film insulation layer (4 layers, 0.1 mm thick).

[0038] This structure utilizes the high-temperature resistance and corona resistance of polyimide to suppress the propagation of corona from the inner and outer conductor surfaces into the insulating layer, and leverages its high dielectric constant to reduce the electric field strength near the conductor. The polypropylene layer provides high insulation strength. The outer conductor is formed by wrapping approximately 13 μm thick aluminum foil. The outermost layer is a protective layer composed of a polyimide film and a polypropylene film, providing mechanical protection.

[0039] Coil assembly 150 presents two key connection methods:

[0040] Three involute parallel configuration: Three coaxial cables of involute length are connected together at the low-voltage end to a low-voltage electrode 110 integrated in a three-way slot to achieve current sharing; the high-voltage end is output through a modular series interface (inner / outer conductor connection sleeve). The insulation support uses insulators 120 in conjunction with elastic pads 140 to resist vibration stress.

[0041] Axial series structure: 15 PFN modules 100 are cascaded and stacked in a straight line via high-voltage electrodes 130 and low-voltage electrodes 110. The overall insulation medium is SF6 gas at 3-5 atmospheres (insulation strength ≥ transformer oil), and the supporting component is insulator 120, with a bulk breakdown field strength of 1.6MV / cm (10ns pulse) and a vacuum surface withstand voltage of 85kV / cm. The final series output withstand voltage is greater than 1MV, power is 5GW, pulse width is 30ns, and leading edge is 5-7ns.

[0042] The PFN module 100 integrates a ring-shaped multi-stage gas switch. This switch employs a 400mm diameter ring electrode layout to increase the ablation area and achieves a repetitive 50Hz operation through forced air cooling. The switch design incorporates mismatch prevention measures: reducing electrode energy storage resistance to suppress "trigger failure" and optimizing the electric field gradient to eliminate "false breakdown." Its output characteristics are excellent: voltage jitter less than 3%, transmission efficiency higher than 90%, and lifespan exceeding 1 million pulses. High-voltage pulses are transmitted via a 75kV thin-film coaxial cable with a withstand voltage of 100kV / mm. The cable penetrates the pulse power source interface flange 301, with its inner conductor directly connected to the electron emitter support rod 319. The interface employs a double-sealing ring structure: an outer metal seal maintains vacuum, while an inner insulator 120 blocks surface discharge.

[0043] In the SF6 gas-filled tank 200, the working pressure is 3-5 atm, and the tank material is non-magnetic stainless steel. Its insulation strength is no less than that of transformer oil, but its weight is only 3% of that of traditional oil media, with a total tank weight of less than 30 kg. The core of the insulation system uses polyimide (PI), and its support components replace plexiglass (PMMA), which has creep resistance and can withstand high temperatures up to 150℃. The PI material has a bulk breakdown field strength of 1.6 MV / cm (10 ns pulse) and a vacuum surface withstand voltage of 85 kV / cm (with grooved design).

[0044] The integrated interfaces cover four main categories of components: mechanical docking, electrical connection, vacuum sealing, and thermal management, ensuring the system works in tandem.

[0045] Mechanical docking: The PFN tank 500 is bolted to the outer cylinder 305 of the microwave source's coil magnetic field via a flange assembly, and the coil magnetic field is used to dock the flange 304 for fixation.

[0046] Key interfaces include: pulse power source interface flange 301 (three-layer composite structure: non-magnetic stainless steel flange, polyimide insulating bushing, copper-tungsten alloy conductive ring), concentric flange 302 (built-in laser alignment module to ensure that the deviation between the coaxial cable and the electron gun axis is less than 0.1mm), flange assembly fixed by concentric bolts 303 (preload self-adjusting bolts to prevent vibration loosening), and magnetic yoke support flange 103 (permalloy magnetic shielding layer to isolate electromagnetic interference from the magnetic field coil).

[0047] Electrical connection: The high voltage pulse (1.125MV) is transmitted to the graphite electron emitter (surface field emission coating, threshold field strength 5kV / mm) via the electron emitter support rod 319 (made of chromium zirconium copper, with high conductivity >90% IACS and withstand voltage gradient of 200kV / cm).

[0048] The output electrode 320 of the ring switch is detachable, and the contact resistance when plugged into the support rod is less than 1mΩ.

[0049] The magnetic field coil (solenoid structure, field strength 0.5T) is used to focus the electron beam and must be kept at a distance of at least 200mm from the PFN tank 500 and electromagnetic isolation measures must be taken.

[0050] Vacuum and Insulation: Multiple sealing and insulation measures ensure safety.

[0051] The 313 space corrugated waveguide uses a double-channel metal "C"-shaped vacuum seal to maintain a vacuum of 10⁻⁴ Pa (helium leakage rate <10⁻⁹ Pa·m). 3 / s);

[0052] The SF6 filling tank 200 uses fluororubber sealing rings (resistant to SF6 corrosion, leakage rate <0.1% / year); electrical isolation is achieved by PI insulating bushings and alumina ceramic rings (collecting electrodes, vacuum surface withstand voltage 120kV / cm).

[0053] Thermal Management and Electromagnetic Shielding: The PFN tank 500 is equipped with a μ-metal shielding layer and is equipotentially connected to the magnetic shielding cover to suppress stray magnetic field interference with the electron beam trajectory. A cooling water interface provides cooling for the magnetic field coil and gas switch (dual-loop titanium alloy piping, flow rate 20L / min). A PI heat insulation sleeve (temperature rise ΔT < 5℃) is installed between the water pipe and the PFN tank 500, and a bellows compensator (axial expansion ± 5mm) is provided to compensate for thermal deformation. The electron gun support rod is made of a low-expansion alloy (CTE = 5 × 10⁻⁶). -6 / ℃). A removable maintenance flange with a quick-lock mechanism is provided for easy maintenance of the gas switch (opening and closing time <5min).

[0054] The structural support includes a non-magnetic stainless steel thick-walled coil magnetic field outer cylinder 305 (thickness 25mm, fixed surface of PFN tank 500), a split carbon fiber reinforced axial support ring (compressive strength 800MPa), a radial positioning base with vibration damping rubber pads (damping coefficient 0.15) fixed to the vehicle platform to suppress vibration, and a ceramic insulated waveguide support frame (creep distance along the surface >500mm, fixing a rectangular output waveguide and electrically isolating it from PFN tank 500).

[0055] The coil magnetic field 306 is entirely encapsulated within the outer cylinder 305, with its axial ends secured by coil magnetic field fastening flanges 308 to ensure the magnet's vibration resistance and stability. A coil magnetic field outer cylinder flange 307 is welded to the end of the outer cylinder 305. This flange's end face is rigidly connected to the coil magnetic field mating flange 304 via bolts, forming a primary sealing surface. A mating flange 309 is embedded in the groove of the mating flange 304, with a mating gasket 318 (tolerance ±0.1mm) between them for precise alignment and vacuum isolation. Finally, the microwave source and the coil magnetic field fastening flange 308 penetrate the mating flange 304, locking the entire coil magnetic field 306 module to the outer shell of the microwave generation system 300. It maintains coaxial positioning (deviation <0.1mm) with the microwave source output waveguide 400 and the antenna interface flange. An antenna channel is connected to the microwave source and antenna channel interface flange 410 at the end of the microwave source output waveguide 400.

[0056] The spatial corrugated waveguide 313 serves as the core channel for electron beam-microwave conversion. Its front end is nested with the tapered interface of the microwave source output waveguide 400 via a spatial pre-waveguide clamp 315, achieving low-loss transmission of 2.45GHz microwaves (VSWR < 1.2). The outer wall of the waveguide is entirely fitted into the spatial waveguide outer cylinder 316, with a 2mm thick boron nitride ceramic insulating ring filling the gap for high-voltage isolation. Spatial corrugated waveguide fasteners 314 penetrate the waist-shaped grooves on the side wall of the waveguide outer cylinder 316, distributed at three points (120° apart). The corrugated waveguide 313 is radially locked to ensure coaxiality deviation <0.05mm; the tungsten needle cathode (0.3mm in diameter) of the electron emitter 317 is axially inserted from the end of the corrugated waveguide 313, and its base is suspended and fixed at the center of the waveguide by two alumina ceramic electron emitter support rods 319, maintaining a dynamic gap of 1.5mm with the output electrode 320 of the ring switch, and exciting the electron beam under a pulse voltage of 1.125MV; the entire waveguide assembly is pressed with the coil magnetic field mating gasket 318 through the end flange to form a vacuum seal (10 -6 (Pa level) and the synergistic effect region of magnetic-electric composite field.

[0057] In one embodiment of the present invention, the following microwave generation path is provided: a high-voltage pulse drives a graphite electron emitter to generate an electron beam. After the electron beam is accelerated in a vacuum diode cavity 202, it bombards a spatial corrugated waveguide (period 12mm, depth 2mm) to generate 2.45GHz microwaves. The microwaves are converted into the desired mode by a TM01-TE11 mode converter 204 (gradual radius spiral structure, conversion efficiency >98%), and finally output through a rectangular output waveguide 205 (section 62mm×124mm, WR975 standard).

[0058] The core working principle of a modular solid-state pulse forming network (PFN) system is to efficiently store and shape the electrical energy of a primary energy source (usually a charging power source) into a high-power nanosecond-level high-voltage square wave pulse, and directly drive a microwave source to generate high-power microwaves.

[0059] The entire process can be broken down into the following key stages:

[0060] Energy storage and slow charging phase: The primary charging power supply charges 15 PFN modules 100 connected in series relatively slowly (compared to pulse discharge time) through the low-voltage side.

[0061] At the core of each PFN module 100 is three involute high-energy-density coaxial cables symmetrically distributed at 120°.

[0062] The charging current flows in through the low-voltage electrode 110, passes through the outer conductor of the cable (metal braided layer / aluminum foil), and then flows to the low-voltage end of the next module through the series interface between modules (high-voltage electrode 130-low-voltage electrode 110 cascaded), finally forming a circuit.

[0063] During charging:

[0064] Cables function as distributed energy storage elements: electrical energy is stored in the form of an electrostatic field within the cable's composite film insulation medium (inner PI - main PP - outer PI). The multilayer polypropylene (PP) film provides extremely high bulk insulation strength and energy storage density (25 times higher), while the inner and outer polyimide (PI) films effectively suppress the initiation and development of corona on the surfaces of the inner and outer conductors, and optimize the electric field distribution near the conductors using their high dielectric constant, thus improving insulation reliability.

[0065] Three involute parallel current sharing: The three cables are connected in parallel at the low-voltage end through the three-phase low-voltage electrode 110, which ensures that the charging current is evenly distributed among the three cables and avoids local overload.

[0066] Modular Serial Boost: 15 identical PFN modules are stacked in series 100 axially.

[0067] At the end of charging, each module bears a portion of the total charging voltage (approximately 75kV), which eventually accumulates at the end of the series chain (high voltage end) to reach the target charging voltage (1.125MV).

[0068] Pulse formation and leading edge sharpening stage (switch triggering and conduction):

[0069] When the charging voltage reaches the preset value, the ring-shaped multi-stage gas switch integrated at the end of the PFN module 100 is triggered.

[0070] Rapid switching: The ring-shaped multi-stage gas switch changes from a high-resistance state to a low-resistance state in an extremely short time (nanosecond level), which is equivalent to connecting the end (high-voltage end) of the PFN module 100 to the energy transmission system (coaxial transmission link) and the load (microwave source electron gun) through the ring-shaped multi-stage gas switch.

[0071] Pulse formation: The characteristic impedance and electrical length of the PFN module 100 (a transmission line network consisting of PFN modules 100 in series and cables) determine the shape and width of the pulse.

[0072] At the instant the toroidal multi-stage gas switch is turned on, the energy stored in the PFN distributed capacitor begins to be released to the load in the form of electromagnetic waves. Since the PFN module 100 is designed to generate square wave pulses, the superposition effect of the discharge of its various energy storage units (cable segments) forms a voltage pulse close to a square wave (designed pulse width 30ns) at the load end.

[0073] Leading-edge compression (pulse passivation): The toroidal multistage gas switch itself features extremely fast turn-on speed and low inductance design (toroidal layout, multistage shortened gap conduction time, forced air cooling to ensure repetition frequency stability). Its "anti-mismatch design" (reducing electrode energy storage resistance and optimizing electric field gradient) effectively avoids "touch without triggering" and "false breakdown," ensuring that the switch closes at an extremely fast speed at a precise moment.

[0074] The rapid turn-on of the ring-shaped multi-stage gas switch is crucial for the rising edge of the compression pulse, sharpening the pulse leading edge to within 5-7ns (or even <5ns) to meet the requirements for efficiently driving microwave sources.

[0075] High-voltage pulse transmission stage: After the ring multi-stage gas switch is turned on, the resulting 1.125MV high-voltage pulse is transmitted to the microwave source through a low-inductance, low-loss coaxial transmission link.

[0076] Transmission path: The pulsed current is output through a ring-type multi-stage gas switch and transmitted via the inner conductor of a 75kV thin-film coaxial cable. This cable penetrates the center of the pulse power source interface flange 301 (which has a three-layer composite structure to ensure high-voltage insulation, vacuum sealing, and electrical connection).

[0077] Precision alignment and low-loss transmission: The concentric flange 302 ensures that the transmission cable and the electron gun axis of the microwave source are highly coaxial (deviation <0.1mm), minimizing reflections and losses caused by mismatch (transmission efficiency >90%). The inner conductor of the cable is ultimately directly connected to the electron emitter support rod 319 (chromium zirconium copper material, high conductivity, high withstand voltage gradient) inside the microwave source.

[0078] Microwave generation stage (electron beam generation, acceleration, and microwave conversion):

[0079] Electron beam emission: A high-voltage pulse is transmitted to the graphite electron emitter via the electron emitter support rod 319. Under the influence of an extremely high pulsed electric field (surface field strength reaches or exceeds the threshold of 5 kV / mm), the graphite cathode generates strong field emission, forming a high-density electron beam current (current density reaches 10 kA / cm²) in the anode-cathode gap of the vacuum diode cavity 202 (cathode: graphite emitter, anode: collector). 2 ).

[0080] Electron beam acceleration: Under the 1.5MV withstand voltage environment of the diode cavity, electrons emitted from the cathode are accelerated by pulsed high voltage and obtain extremely high energy, forming a high-speed electron beam.

[0081] Electron beam focusing: The magnetic field coil generates a strong axial magnetic field (0.5T) to focus the high-speed electron beam, keeping it with a small beam diameter, so that it can accurately bombard the subsequent microwave generating structure.

[0082] Microwave excitation and transmission: The focused high-energy electron beam passes through the hole (or grid) on the collector and enters the spatial corrugated waveguide.

[0083] When an electron beam moves in a spatial corrugated waveguide (with a periodic corrugated structure on the inner wall, a period of 12 mm, and a depth of 2 mm), its energy is converted into microwave energy through interaction with the electromagnetic field inside the waveguide (mechanisms such as stimulated emission / Cherenkov radiation), generating microwaves of a specific frequency (such as 2.45 GHz).

[0084] Mode Conversion and Output: The microwave mode (such as the TM01 mode) excited in the spatial corrugated waveguide is converted into the TE11 mode commonly used in rectangular waveguides by the TM01-TE11 mode converter 204 (gradual radius spiral structure, conversion efficiency >98%). Finally, the microwave is output to the system through the rectangular output waveguide 205 (WR975 standard).

[0085] System support and assurance (throughout the entire process):

[0086] Lightweight insulation and encapsulation: The SF6 gas-filled tank 200 (3-5 atm) provides a high-insulation-strength (≥ transformer oil) and lightweight (only 3% of the weight of conventional oil-based media) environment for the entire series-connected PFN module 100.

[0087] Polyimide (PI) insulation systems (support components, insulators 120, tape) are used for insulation and support inside modules, between modules, and at interfaces. Their high volume breakdown field strength (1.6MV / cm) and high vacuum surface withstand voltage (85kV / cm, enhanced by grooved design) are the foundation for the reliable high-voltage operation of the system.

[0088] Thermal management: The toroidal gas switch maintains a 50Hz operating frequency through forced air cooling; the electron gun's magnetic field coil and collecting electrode are cooled via a water-cooled piping interface (dual-loop titanium alloy piping, 20L / min); the air-cooling and water-cooling systems operate in parallel. PI insulation sleeves, bellows compensators, and low-expansion alloy (CTE=5×10⁻⁶ / ℃) support rods are designed to manage thermal deformation.

[0089] Vacuum maintenance: The microwave generation area (space corrugated waveguide, mode converter, output waveguide, and part of the diode area) needs to maintain a high vacuum (10⁻⁴ Pa), which is ensured by a double-channel metal "C"-shaped vacuum seal (extremely low helium leakage rate) and a dynamic sealing ring 108. The SF6 filling tank 200 is independently sealed by a fluororubber O-ring (resistant to SF6 corrosion and with a low annual leakage rate).

[0090] Mechanical stability and electromagnetic compatibility: The bolted flange assembly (including preload self-adjusting bolts), radial positioning base (with vibration damping rubber pads), and axial support ring (carbon fiber reinforced frame) ensure the mechanical stability of the system in the vehicle environment (resistance to 6 degrees of freedom vibration).

[0091] The PFN tank 500 is equipped with a μ-metal shielding layer, a permalloy magnetic shielding layer for the magnetic yoke support 103, a magnetic shielding cover (equipotential with the tank), and a design that ensures the PFN tank 500 is more than 200mm away from the magnetic field coil. This effectively isolates the PFN electromagnetic interference from affecting the electron beam focusing magnetic field and trajectory. The equipotential bonding design avoids discharge caused by potential differences.

[0092] In summary, the system efficiently stores electrical energy through a modular, series-connected, three-involute parallel PFN structure based on high-energy-density composite insulated cables. It then utilizes a low-inductance, fast-response ring-type multi-stage gas switch for precise triggering and rapid conduction, releasing the stored energy and generating a 1.125MV high-voltage square wave pulse with an extremely steep leading edge (<7ns) and a fixed pulse width (30ns). This high-voltage pulse is efficiently (90%) transmitted to the field emission cathode of the microwave source via a precisely designed low-loss coaxial transmission link. Under the action of the high-voltage pulse, the cathode emits a high-current electron beam. After being accelerated by high voltage and focused by a magnetic field in a vacuum, the electron beam bombards a specially structured spatial corrugated waveguide 313, converting its kinetic energy into microwave energy. The generated microwaves are then optimized by a mode converter and output through a standard waveguide.

[0093] Throughout the process, the lightweight SF6 insulation, high-performance PI insulation system, multiple seals, efficient thermal management, and precise electromagnetic shielding / mechanical support design jointly ensured the system's high power output (5GW), high reliability, and lightweight (total weight <500kg) in the vehicle environment.

[0094] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A high-power microwave system based on a modular loop line, characterized in that, It includes a pulse power source and a microwave generation system. The pulse power source is connected to the microwave generation system through an SF6 gas-filled tank. The pulse power source consists of 15 PFN modules connected in series axially, with the PFN tank located outside the series-connected PFN modules. Each PFN module includes a coil assembly, low-voltage electrodes, high-voltage electrodes, insulators, and elastic pads. The coil assembly includes three involute coaxial cables, which are symmetrically distributed at 120° to the three low-voltage electrodes. The high-voltage electrodes are secured to the inner conductor of the cables via a threaded metal connecting sleeve. The low-voltage electrodes are connected to the outer conductor of the cables via a threaded outer conductor connecting sleeve. An elastic pad made of EPDM rubber is placed between the high-voltage electrodes and the coil assembly. Insulators isolate the high- and low-voltage electrodes. The microwave generation system converts high-power electrical pulses from the pulse power source into high-power microwave energy and outputs it.

2. A high-power microwave system based on a modular loop line according to claim 1, characterized in that, Coaxial cables consist of an inner conductor, a thin-film insulation layer, and an outer sheath. The inner conductor is made of aluminum rod. The thin-film insulation layer consists of, from the inside out: an inner polyimide tape insulation layer, a polypropylene film insulation layer, and an outer polyimide film insulation layer. The outer sheath covers the outer wall of the outer conductor.

3. A high-power microwave system based on a modular loop line according to claim 2, characterized in that, The microwave generating system also includes a coil magnetic field, which is encapsulated inside an outer cylinder. The axial ends of the outer cylinder are secured by coil magnetic field fastening flanges. An outer cylinder flange is welded to the end of the outer cylinder. The outer cylinder flange and the coil magnetic field mating flange are rigidly connected by bolts. The mating flange is embedded in the groove of the mating flange. A mating gasket is provided between the mating flange and the mating flange. The mating gasket is used for precise alignment and vacuum isolation.

4. A high-power microwave system based on a modular loop line according to claim 3, characterized in that, The microwave generating system also includes a microwave source and coil magnetic field fastening flange, which passes through and matches the coil magnetic field docking flange to lock the coil magnetic field to the outer shell of the microwave generating system and maintains coaxial positioning with the microwave source output waveguide and antenna interface flange. At the end of the microwave source output waveguide, the microwave source and antenna channel interface flange is connected to an antenna channel.

5. A high-power microwave system based on a modular loop line according to claim 4, characterized in that, The microwave generation system also includes a spatial corrugated waveguide, which serves as the core channel for electron beam-microwave conversion. The front end of the spatial corrugated waveguide is connected to the microwave source output waveguide via a spatial pre-waveguide clamp. The outer wall of the spatial corrugated waveguide is inserted into the outer cylinder of the spatial waveguide, and the spatial corrugated waveguide is radially locked in a three-point evenly distributed manner by fasteners that pass through the waist-shaped grooves on the side wall of the outer cylinder of the spatial waveguide.

6. A high-power microwave system based on a modular loop line according to claim 5, characterized in that, A tungsten needle cathode is axially inserted into the electron emitter from the end of the spatial corrugated waveguide. The base of the spatial corrugated waveguide is suspended and fixed at the center of the spatial corrugated waveguide by two alumina ceramic electron emitter support rods.

7. A high-power microwave system based on a modular loop line according to claim 6, characterized in that, The spatial corrugated waveguide is pressed together with the coil magnetic field through the end flange and the gasket, forming a vacuum seal and a synergistic effect zone of the magnetic-electric composite field.

8. A high-power microwave system based on a modular loop line according to claim 7, characterized in that, The SF6 filling tank uses fluororubber sealing rings, and electrical isolation is achieved by PI insulating bushings and alumina ceramic rings.

9. A high-power microwave system based on a modular loop line according to claim 8, characterized in that, The high-voltage pulse is transmitted to the graphite electron emitter via the electron emitter support rod. The graphite electron emitter generates an electron beam, which is accelerated in the vacuum diode cavity and then bombards the space ripple waveguide.

10. A high-power microwave system based on a modular loop line according to claim 9, characterized in that, The spatial corrugated waveguide uses a double-channel metal "C"-shaped vacuum seal to maintain 10 -4 In a vacuum of Pa, when an electron beam moves through a spatially corrugated waveguide, its energy is converted into microwave energy through interaction with the electromagnetic field within the waveguide, generating microwaves of a specific frequency.

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